(1.) Field of the Invention
The present invention relates to an optical information recording and/or reproducing apparatus in which optical information is recorded and/or reproduced with the aid of an information recording medium such as an optical card. In the apparatus according to the invention, the optical card and an optical head are moved relatively in a track direction, which is parallel to the extending direction of tracks formed on the optical card, to record optical information on the optical card and/or reproduce optical information recorded on the optical card; additionally the relative moving speed between the optical card and the optical head is controlled at a given speed in order to prevent errors in recording and/or reproducing optical information on the optical card.
(2.) Prior Art Statement
On the optical information recording medium such as an optical card, it is impossible to rewrite optical information, which had already been written thereon. But the optical card has a great memory capacity, i.e. about several thousand times to ten thousand times as large as that of a magnetic card. The optical card has its memory capacity of about from one to two mega bytes, so that a great number of applications such as a bankbook, a pocket map and a prepaid card for shopping can be considered.
Many optical card constructions have been suggested; and one of the constructions of the optical card, which has been suggested by the applicant in Japanese Preliminarily Laid-open Publication No. 63-37876, is shown in FIG. 1. On the optical card 11, there is provided an optical information recording portion 12. The optical information recording portion 12 comprises a plurality of tracks 13 which are formed in a longitudinal direction of the optical card 11, being parallel to each other. On both sides of the optical information recording portion 12, there are arranged ID portions 14A and 14B, respectively. In each ID portion 14A and 14B, address information corresponding to each track 13 is recorded. Since the ID portions 14A and 14B are provided on both sides of the optical card 11, the address information recorded thereon can be read out even when the optical card 11 is moved with respect to the optical head either from right side to left side or from left side to right side. As is apparent from FIG. 1, the ID portions 14A and 14B are arranged inside by a given distance, for instance 4 mm, from both ends of the optical card 11 in order to prevent the influence of a defect or dirt formed on the edge portions of the optical card 11 and in order to relatively move the optical card and the optical head at a constant speed between ID portions 14A and 14B. When recording and/or reproducing optical information on the optical card 11 from left to right (forward direction), the address information recorded on the left side ID portion 14A is read out to identify the position of the optical head with respect to the optical card; and when recording and/or reproducing optical information on the optical card 11 from right to left (backward direction), the address information recorded on the right side ID portion 14B is read out.
FIG. 2 is a block diagram showing the whole construction of a conventional optical information recording/reproducing apparatus. In the apparatus shown in FIG. 2, it is arranged such that an optical card 11 is reciprocally transferred in a track direction, which extends parallel to the tracks formed on the optical card 11, and an optical head 21 is moved in a tracking direction, which is perpendicular to the track direction, to record optical data on the optical card 11 and/or reproduce optical data recorded on the optical card 11. The optical card 11 is mounted on a shuttle 24 which is arranged on a transfer belt 23. The transfer belt 23 is passed round pulleys 22A and 22B. The shuttle 24 is arranged to be reciprocally transferred in the track direction by means of a motor 26. The moving speed of the shuttle 24 is controlled by a motor servo circuit 25 made constant at a predetermined speed. A rotary encoder 27 is arranged to a shaft of the motor 26 in order to detect a position of the shuttle 24 with respect to the optical head 21. It is arranged such that one pulse of the rotary encoder 27 corresponds to 50 .mu.m of a moving distance of the shuttle 24. Positional information of the shuttle 24 is supplied to a controller 28 via the motor servo circuit 25; and the controller 28 supplies an order to said motor servo circuit 25 to move the shuttle 24 at a given constant speed during which a light beam emanated from the optical head 21 is traced onto the information recording area 15, provided between ID portions 14A and 14B.
FIG. 3 is a block diagram showing a circuit construction of the motor servo circuit 25. The motor servo circuit 25 comprises a ROM 25A, a D/A converter 25B, a subtracter 25C, a motor driving circuit 25B, an F/V converter 25E, a direction discriminator 25F and an up and down counter 25G.
The shuttle 24 is reciprocally moved in the track direction by means of the motor 26. In the ROM 25A, when a driving signal S1 and a driving direction signal S2 for determining the moving direction of the shuttle 24 is supplied from the controller 28, an address of the ROM 25A is determined. One address in ROM 25A is arranged to correspond to a moving distance of 50 .mu.m of the shuttle 24. Then a driving data (target speed) of the shuttle 24 memorized in ROM 25A is supplied to the motor 26 via the D/A converter 25B and the motor driving circuit 25D. The shuttle 24 is moved in the forward direction in response to the signal from ROM 25A; thereafter an A phase output or B phase output of the rotary encoder 27, which is provided on the same shaft of the motor 26, is supplied to the direction discriminator 25D; additionally an output of the discriminator 25D is supplied to the F/V convertor 25E and the up and down counter 25G. In the up and down counter 25G, whose output indicates the position of the shuttle 24 with respect to the optical head 21, the counted value is made clear when the phase of the output of the direction discriminator 25D is changed. The output of the F/V convertor 25E is further supplied to a subtracter 25C, in which a difference between the output of the F/V convertor 25E and the D/A convertor 25B is detected. The rotation of the motor 26, i.e. the moving speed of the shuttle 24, is controlled in the motor driving circuit 25D so as to make the difference zero. In such manner, the moving speed of the shuttle 24 is controlled at the target speed during which the optical head 21 is moved between the ID portions 14A and 14B.
From the ROM 25A, output data is supplied to the motor driving circuit 25D such that: when the shuttle 24 is moved such that the optical head 21 passes a left side accelerating area of the optical card 11, i.e. left side area of the left side ID portion 14A, the shuttle 24 is moved to be accelerated, then after the optical head 21 passes over the left side accelerating area of the optical card 11, in other words, after the number of pulses counted in the up and down counter 25G becomes higher than a predetermining value representing that the optical head 21 passes over the accelerating area of the optical card 11, the shuttle 24 moves at a constant speed between the left side ID portion 14A and the right side ID portion 14B; when the optical head 21 becomes to the right side decelerating area, i.e. right side area of the right side ID portion 14B, the shuttle 24 is decelerated. Thereafter, data representing that the movement speed of the shuttle is zero are supplied from the ROM 21A to the motor driving circuit 25D to stop the shuttle 24 when the member of pulses counted in the up and down counter 25G becomes to a given value.
In order to transfer the shuttle 24 in the backward direction, the reversed driving direction signal and the driving signal may be supplied to ROM 25A of the motor servo circuit 25 from the controller 28.
The optical head 21 comprises a laser diode 21A as a light source, a collimator lens 21B, a prism 21C, an objective lens 21D and a photodetector 21E. The laser beam for writing/reading information emanated from the laser diode 21A is made incident upon the optical card 11 via the collimator lens 21B, the prism 21C and the objective lens 21D; and then the light beam is reflected by the optical card 11 and made incident upon the photodetector 21E after the direction thereof is changed 90 degrees by means of the prism 21C.
The output of the photodetector 21E is supplied to a demodulating circuit 29 to obtain an information reproducing signal therefrom and the output is also supplied to a focusing and tracking servo circuit 30 to detect a focusing error signal and a tracking error signal. The optical head 21 is driven in focusing and tracking directions in accordance with the focusing error signal and the tracking error signal detected by the focusing and tracking servo circuit 30 in order to let the incident light beam always trace on the track 13 in a focused condition.
The controller 28 is connected to the laser diode 21A via a laser diode driving circuit 31. When information data recorded on the optical card 11 is read out, the laser diode driving circuit 31 supplies an order to the laser diode 11 to produce a light beam having a low power for reading information recorded on the optical card 11 under the control of the controller 28. The controller 28 is also connected to the motor servo circuit 25, the demodulating circuit 29 and the focusing/tracking servo circuit 30. The driving modes of these circuits are controlled by the controller 28 such that a desired track is sought in accordance with track address information demodulated by the demodulating circuit 29 to reproduce optical information recorded on the relevant track and/or to record optical information thereon.
When optical information is recorded on the optical card 11, a laser beam, which is modulated in accordance with the writing data, having a high power emitted from the laser diode 21A via the laser driving circuit 31 is illuminated on the optical card 11, after the relevant track is sought.
In the conventional optical information recording/reproducing apparatus described above, when the driving direction of the shuttle 24 is turned, the shuttle 24 is stopped once; in other words, the moving speed of the shuttle 24 is controlled so as to become zero when the driving direction is changed. However, if a defect such as dust and flaw is formed on a stopping position of the shuttle 21 where the light beam emanated from the optical head 21 is illuminated, the tracking error signal would not be obtained correctly due to the defect. Therefore, the tracking servo system of the apparatus cannot serve normally, so that the light beam cannot trace the desired track.